Drip irrigation systems have been used to supply water and/or irrigation liquids such as liquid fertilizer to the plants grown on the soil in the agricultural land, plantation and the like.
Such a drip irrigation system includes a pump for pumping up water from the water source, a filter, a fertigation device (chemigation device if necessary), a back flow prevention device, a main pipe, an elongated drip watering tube connected to the terminal of the main pipe, and the like. The drip watering tube is laid on the soil on which plants are grown.
The drip watering tube is configured to eject a predetermined amount of irrigation liquid in the tube main body per unit time (i.e., at a predetermined ejection rate) from a plurality of ejection ports bored in the elongated tube main body at predetermined intervals along the length of the tube main body, to slowly supply the irrigation liquid (i.e., to perform drip irrigation) to the soil outside the drip watering tube.
The use of the drip watering tube enables one not only to save water and fertilizer but also to supply water at a moderate supply rate. In addition, the oxygen required for plant roots can be ensured in the soil. Thus, growing of plants can be favorably managed.
In such a drip watering tube, a plurality of drip irrigation drippers for controlling the ejection amount of the irrigation liquid from each of ejection ports per unit time are provided at the respective ejection ports.
In this drip irrigation dripper, water flowing in the tube main body flows into the drip irrigation dripper through the inflow port and flows through a pressure reduction channel (labyrinth) inside the drip irrigation dripper in such a manner that the pressure of the irrigation liquid is reduced, and then, the irrigation liquid is ejected from the ejection port communicated with the downstream side of the pressure reduction channel.
Some drip irrigation drippers are provided with a so-called differential pressure control mechanism (pressure correction function). Such drip irrigation drippers of this type have for example a three-component structure in which an elastic film (for example, silicone rubber) such as a diaphragm is sandwiched by an inflow side member and an ejection side member, as with the drip irrigation dripper (emitter unit) disclosed in PTL 1.
As disclosed also in paragraph [0004] of PTL 1, the drip irrigation dripper of this type is designed such that the ejection amount of the irrigation liquid from the drip irrigation dripper (emitter) has substantially no relation with the variation in pressure of the irrigation flow supplied to the drip irrigation dripper.
Therefore, the drip irrigation dripper of this type has been expected to suppress non-uniformity in the ejection amount of the irrigation liquid between the drip irrigation drippers disposed on the upstream side (high pressure side) and those disposed on the downstream side (low pressure side) in the tube main body, to thereby equalize the grow rate of plant on the entire soil. cl CITATION LIST